Logging, Error Reporting & Diagnostics
Build a logging and error-reporting layer so you can diagnose problems in extensions running on real users' machines.
Logging, Error Reporting & Diagnostics is a free Browser Extensions Development (Chrome & Edge) lesson on CoddyKit — lesson 4 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Browser Extensions Development (Chrome & Edge) learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
You Cannot Watch Every Console
Once your extension ships, you cannot open dev tools on every user's browser. A deliberate logging and error-reporting strategy is how you learn what is going wrong in the wild.
A Central Log Function
Wrap logging in one function so you can change behavior in a single place, add timestamps, and silence output in production.
function log(level, msg) {
console[level]('[MyExt] ' + new Date().toISOString() + ' ' + msg)
}Log Levels
Use distinct levels so you can filter noise. Common ones: debug, info, warn, and error.
log('warn', 'Quota nearly full')
log('error', 'Sync failed')Catching Uncaught Errors
Add a global error handler in each context to capture exceptions you did not anticipate.
self.addEventListener('error', (e) => {
log('error', e.message + ' @ ' + e.filename)
})Catching Rejected Promises
Unhandled promise rejections are a common silent failure. Listen for unhandledrejection too.
self.addEventListener('unhandledrejection', (e) => {
log('error', 'Unhandled: ' + e.reason)
})Persisting a Log Ring Buffer
Keep the last N log entries in storage so users can export them when reporting a bug. Cap the size to avoid filling the quota.
async function persist(entry) {
const { logs = [] } = await chrome.storage.local.get('logs')
logs.push(entry)
if (logs.length > 200) logs.shift()
await chrome.storage.local.set({ logs })
}Letting Users Export Logs
Add an options-page button that dumps stored logs to a downloadable file, making support requests far more useful.
const blob = new Blob([JSON.stringify(logs, null, 2)], { type: 'application/json' })
const url = URL.createObjectURL(blob)
chrome.downloads.download({ url, filename: 'myext-logs.json' })Remote Error Reporting
For aggregate insight, POST anonymized error reports to your own endpoint. Always make this opt-in and strip personal data.
fetch('https://errors.example.com', {
method: 'POST',
body: JSON.stringify({ msg, version })
})Respecting Privacy
Never log page contents, URLs with tokens, or anything sensitive. Disclose any remote reporting in your privacy policy and store listing.
Silencing Logs in Production
Gate verbose logging behind a debug flag so release builds stay quiet and fast, while you can flip it on when investigating.
const DEBUG = false
function debug(msg) { if (DEBUG) log('debug', msg) }Correlating Across Contexts
Tag each log with its source (popup, content, worker) so you can trace a bug that spans contexts and messaging.
log('info', '[worker] received PING')Quick Check
Test your diagnostics knowledge.
Recap
You built a diagnostics layer:
- Central log function with levels
- Global
errorandunhandledrejectionhandlers - A capped log buffer in storage with export
- Opt-in, privacy-safe remote reporting
- A debug flag and per-context tagging
Good diagnostics turn mysterious field bugs into fixable reports.
Frequently asked questions
Is the “Logging, Error Reporting & Diagnostics” lesson free?
Yes — the full text of “Logging, Error Reporting & Diagnostics” is free to read here on the web, and the Browser Extensions Development (Chrome & Edge) course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Browser Extensions Development (Chrome & Edge) course, upgrade to CoddyKit PRO.
What will I learn in “Logging, Error Reporting & Diagnostics”?
Build a logging and error-reporting layer so you can diagnose problems in extensions running on real users' machines. You practise Browser Extensions Development (Chrome & Edge) with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start Browser Extensions Development (Chrome & Edge)?
No prior experience is required. Browser Extensions Development (Chrome & Edge) on CoddyKit is structured for beginners through advanced learners; this is — lesson 4 of 4, so you can start here or from the beginning and move at your own pace.
How long does the “Logging, Error Reporting & Diagnostics” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this Browser Extensions Development (Chrome & Edge) lesson?
Yes. Every Browser Extensions Development (Chrome & Edge) lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- Debugging Extension Components
- Writing Unit Tests for Extensions
- Performance Optimization Strategies
- Logging, Error Reporting & Diagnostics